This invention relates to mobile telephony and, in particular, to an improved dual mode mobile telephone.
A variety of standards have been developed for digital cellular and PCS telephone systems, based on a variety of bandwidth allocation techniques. These include the European time division multiple access (TDMA)-based Global System for Mobile communication (GSM), and the Telecommunications Industry Association (TIA) IS-136 TDMA standard (also known as North American TDMA). TDMA systems allocate unique time slots to each user within a single radio-frequency channel.
Each of these systems has widespread deployment. However, a user of a cellular telephone or PCS device that complies with one standard is inoperable in a network communicating according to another. Thus, typically, a user would need multiple such devices to operate in each such network. Alternatively, “dual-mode” telephones have been developed, in which the telephone is useable in two networks. However, such telephones typically require a complete baseband chipset to be provided for each of the two wireless or cordless standards. This can result in an undesirably long development time for each chipset. Moreover, each such telephone requires a unique design, which can add to development costs.